This invention relates to joint assemblies. It relates in particular to the technical field of vibratory metal forming, and to the connections that must be made between vibration generators and the forming tools that are to be vibrated by them. Such tools may include, for instance, plugs to which axial vibrations are to be applied in the course of plug tube drawing as described in UK Pat. No. 1,380,421 (UKPA No. 7579/71), and internal mandrels to which similar vibrations are to be applied in the course of tube bending as described in the specification of UK patent application No. 8318577.
It is customary for such a plug or mandrel to be mounted at one end of a long bar so that the bar passes with clearance along the full length of the unformed part of the tube that is being drawn or bent, and projects from the free end. The joint to which this invention relates will in practice be the one between that bar and one side or face of a vibratory horn or concentrator, the opposite face of which will carry suitable ultrasonic vibration generators. Such generators, for instance of magnetrostrictive or peizo-electric type, are well known in the art.
Such a joint must be simple to make and unmake, because in use those two operations will have to be made in succession each time the mandrel is changed. It is also essential that the joint should be a very positive one, so that the energy of the vibrators is transmitted to the tool with maximum efficiency, and that the joint should be repeatable so that that efficiency undergoes no change each time the joint is remade after being unmade. Practice has shown that a conventional joint, for instance a screw joint, tends not adequately to meet this combination of requirements, especially when the joint has to be made on the factory floor by staff unfamiliar with ultrasonic forming techniques.